Congestive heart failure (CHF) is a condition in which a weakened heart cannot pump enough blood to body organs. Heart failure may affect either the right side, left side, or both sides of the heart. As pumping action is lost, blood may back up into other areas of the body, including the liver, gastrointestinal tract, and extremities (right-sided heart failure), or the lungs (left-sided heart failure). Structural or functional causes of heart failure include high blood pressure (hypertension), valvular heart disease, congenital heart diseases, cardiomyopathy, heart tumor, and other heart diseases. Precipitating factors include infections with high fever or complicated infections, use of negative inotropic drugs (such as beta-blockers and calcium channel blocker), anemia, irregular heartbeats (arrhythmias), hyperthyroidism, and kidney disease.
CHF can perhaps be arrested, even temporarily remitted, but never cured due to the nature of its most common causes (coronary artery disease leading to myocardial infarction leading to permanently destroyed or damaged myocardial substrate). Therefore, a patient with CHF requires careful and attentive care and disease management, particularly as the disease state progresses. Regarding progressive states of CHF, the New York Heart Association (NYHA) has classified heart condition into four classes: Class I—patients with no limitation of activities; they suffer no symptoms from ordinary activities; Class II—patients with slight, mild limitation of activity; they are comfortable with rest or with mild exertion; Class III—patients with marked limitation of activity; they are comfortable only at rest; and Class IV—patients who should be at complete rest, confined to bed or chair; any physical activity brings on discomfort and symptoms occur at rest. Proper treatment of heart failure often relies on assessment of a patient's classification, see, e.g., Shamsham and Mitchell, “Essentials of the diagnosis of heart failure”, Am. Fam. Phys., Mar. 1, 2000 (pp. 1319–1330). For example, Shamsham and Mitchell present an algorithm for diastolic dysfunction and systolic dysfunction that references the NYHA classes.
While a variety of treatments exist for patients with decompensated CHF, see, e.g., Loh, “Overview: Old and new controversies in the treatment of advanced congestive heart failure”, J. Card. Fail., 7(2 Suppl. 1): 1–7 (2001); and Gomberg-Maitland, et al., “Treatment of congestive heart failure”, Arch. Intern. Med., 161: 342–349 (2001), a need exists for improved treatments, in addition, a need exists for merging treatment and diagnostics.
A physician's ability to treat a patient relies heavily on proper diagnosis of the patient's condition. Diagnosis typically involves categorizing and differentiating between many possible diseases and disease states. In the past, diagnosis usually depended on a physician's ability to use medical texts and personal knowledge together with consultation with other physicians, etc. With the onset of computers and digital databases, a plethora of information has become available to physicians and, in general, to a variety of healthcare workers. However, challenges still exist in managing such a large volume of information. Even greater challenges exist in integrating the information or using the information to create treatment pathways. As an example, a treatment pathway is a patient care algorithm, or path, that is intended to increase efficiency and thereby improve patient care. Thus, while computers have revolutionized storage and availability of information, a need exists for systems and/or methods to assist and/or manage in the diagnosis and/or treatment of disease, such as, but not limited to CHF.
Advances in computer technology have also led to improved implantable cardiac devices (ICDs), which are often indicated for at least some CHF patients. ICDs are implanted within the body of a patient to monitor, regulate, and/or correct heart function. ICDs include implantable cardiac stimulation devices (e.g., implantable cardiac pacemakers, implantable defibrillators) that apply stimulation therapy to the heart as well as implantable cardiac monitors that monitor heart activity.
ICDs typically include a control unit positioned within a casing that is implanted into the body and a set of leads that are positioned to impart stimulation and/or monitor cardiac activity. With improved processor and memory technologies, the control units have become increasingly more sophisticated, allowing them to monitor many types of conditions and apply tailored stimulation therapies in response to those conditions.
ICDs are typically capable of being programmed remotely by an external programming device, often called a “programmer”. Today, individual ICDs are equipped with telemetry circuits that communicate with the programmer. One type of programmer utilizes an electromagnetic wand that is placed near the implanted cardiac device to communicate with the implanted device. The wand contains a coil that forms a transformer coupling with the ICD telemetry circuitry. The wand transmits low frequency signals by varying coil impedance.
Early telemetry systems were passive, meaning that the communication was unidirectional from the programmer to the implanted device. Passive telemetry allowed a treating physician to download instructions to the implanted device following implantation. Due to power and size constraints, early commercial versions of the implanted devices were incapable of transmitting information back to the programmer.
As power capabilities improved, active telemetry became feasible, allowing synchronous bi-directional communication between the implanted device and the programmer. Active telemetry utilizes a half-duplex communication mode in which the programmer sends instructions in a predefined frame format and, following termination of this transmission, the implanted device returns data using the frame format. With active telemetry, the treating physician is able to not only program the implanted device, but also retrieve information from the implanted device to evaluate heart activity and device performance. The treating physician may periodically want to review device performance or heart activity data for predefined periods of time to ensure that the device is providing therapy in desired manner. Consequently, current generation implantable cardiac therapy devices incorporate memories, and the processors periodically sample and record various performance parameter measurements in the memories.
Data pertaining to a patient's cardiac condition is gathered and stored by the programmer during programming sessions and/or follow-up monitoring of the ICDs. Analysis of the cardiac condition is performed locally by the programming software. Programmers offer comprehensive diagnostic capabilities, high-speed processing, and easy operation, thereby facilitating efficient programming and timely patient follow-up.
In addition to local analysis, TransTelephonic Monitoring (TTM) systems are employed to gather current cardiac data from patients who are remote from the healthcare provider. TTM systems are placed in patients' homes. They typically include a base unit that gathers information from the ICD much like the programmer would. The base unit is connected to a telephone network so that data may be transmitted to the medical staff responsible for that patient. An example of an ICD TTM system is a service from St. Jude Medical® and Raytel® Cardiac Services called “Housecall™.” This service provides current programmed parameters and episode diagnostic information for a plurality of events including stored electrograms (EGMs). Real-time EGMs with annotated status information can also be transmitted.
Using a telephone and a transmitter, the TTM system provides both the medical staff and the patient the convenience of instant analysis of therapy without having the patient leave the comfort of home. Typically, real-time measurements are transmitted in just minutes. Patients may be closely monitored, and the medical staff has more control of their patient's treatment, thus administering better patient management.
Another challenge that still persists, however, is how to efficiently and effectively integrate patient information, device information and/or other sources of information to medical personnel and other knowledge workers who might have an interest in the device data. A yet larger challenge involves use such information in creating, implementing and/or maintaining treatment pathways, which optionally include use of an ICD. Indeed, a need exists for systems and/or methods that address these challenges.